What triggers the depolarization of the postsynaptic cell during long-term potentiation?

The correct answer highlights the role of sodium entry through AMPA channels in the depolarization of the postsynaptic cell during long-term potentiation (LTP). In LTP, an increase in synaptic strength occurs following repeated stimulation of a synapse, and one critical event in this process is the activation of AMPA receptors on the postsynaptic membrane.

When the presynaptic neuron releases neurotransmitters, primarily glutamate, these bind to AMPA receptors on the postsynaptic neuron. The binding of glutamate to AMPA receptors opens these channels, allowing sodium ions (Na+) to flow into the postsynaptic cell. This influx of positive charge causes depolarization of the membrane potential, making the neuron more likely to fire an action potential.

This depolarization is crucial for the subsequent activation of NMDA receptors, which are also involved in LTP, as their activation requires both ligand binding and a sufficient depolarization to relieve magnesium block. The opening of AMPA channels thus plays a foundational role in triggering the processes that enhance synaptic strength and facilitate the storage of information in neuronal circuits.

The other choices do not directly relate to the initial depolarization triggered by LTP. For example, inhibition of serotonin